Phase-change material

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A sodium acetate heating pad. When the sodium acetate solution crystallises, it becomes warm.

A phase-change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.

Characteristics and classification[edit]

PCMs latent heat storage can be achieved through solid–solid, solid–liquid, solid–gas and liquid–gas phase change. However, the only phase change used for PCMs is the solid–liquid change. Liquid-gas phase changes are not practical for use as thermal storage due to the large volumes or high pressures required to store the materials when in their gas phase. Liquid–gas transitions do have a higher heat of transformation than solid–liquid transitions. Solid–solid phase changes are typically very slow and have a rather low heat of transformation.

Initially, the solid–liquid PCMs behave like sensible heat storage (SHS) materials; their temperature rises as they absorb heat. Unlike conventional SHS, however, when PCMs reach the temperature at which they change phase (their melting temperature) they absorb large amounts of heat at an almost constant temperature. The PCM continues to absorb heat without a significant rise in temperature until all the material is transformed to the liquid phase. When the ambient temperature around a liquid material falls, the PCM solidifies, releasing its stored latent heat. A large number of PCMs are available in any required temperature range from −5 up to 190 °C.[1] Within the human comfort range between 20–30 °C, some PCMs are very effective. They store 5 to 14 times more heat per unit volume than conventional storage materials such as water, masonry or rock.[2]

Organic PCMs[edit]

Paraffin (CnH2n+2) and fatty acids (CH3(CH2)2nCOOH)[3]

  • Advantages
    1. Freeze without much supercooling
    2. Ability to melt congruently
    3. Self nucleating properties
    4. Compatibility with conventional material of construction
    5. No segregation
    6. Chemically stable
    7. High heat of fusion
    8. Safe and non-reactive
    9. Recyclable
  • Disadvantages
    1. Low thermal conductivity in their solid state. High heat transfer rates are required during the freezing cycle
    2. Volumetric latent heat storage capacity is low
    3. Flammable. This can be partially alleviated by specialist containment
    4. To obtain reliable phase change points, most manufacturers use technical grade paraffins which are essentially paraffin mixture(s) and are completely refined of oil, resulting in high costs

Inorganic[edit]

Salt hydrates (MnH2O)[4]

  • Advantages
    1. High volumetric latent heat storage capacity
    2. Availability and low cost
    3. Sharp melting point
    4. High thermal conductivity
    5. High heat of fusion
    6. Non-flammable
  • Disadvantages
    1. Change of volume is very high
    2. Super cooling is major problem in solid–liquid transition
    3. Nucleating agents are needed and they often become inoperative after repeated cycling

Eutectics[edit]

Organic-organic, organic-inorganic, inorganic-inorganic compounds

  • Advantages
    1. Eutectics have sharp melting point similar to pure substance
    2. Volumetric storage density is slightly above organic compounds
  • Disadvantages
    1. Only limited data is available on thermo-physical properties as the use of these materials are relatively new to thermal storage application

Hygroscopic materials[edit]

Many natural building materials are hygroscopic, that is they can absorb (water condenses) and release water (water evaporates). The process is thus:

  • Condensation (gas to liquid) ΔH<0; enthalpy decreases (exothermic process) gives off heat.
  • Vaporization (liquid to gas) ΔH>0; enthalpy increases (endothermic process) absorbs heat (or cools).

Whilst this process liberates a small quantity of energy, large surfaces area allows significant (1–2 °C) heating or cooling in buildings. The corresponding materials are wool insulation, earth/clay render finishes, etc.

Selection criteria[edit]

  • Thermodynamic properties. The phase change material should possess:[5]
    1. Melting temperature in the desired operating temperature range
    2. High latent heat of fusion per unit volume
    3. High specific heat, high density and high thermal conductivity
    4. Small volume changes on phase transformation and small vapor pressure at operating temperatures to reduce the containment problem
    5. Congruent melting
  • Kinetic properties
    1. High nucleation rate to avoid supercooling of the liquid phase
    2. High rate of crystal growth, so that the system can meet demands of heat recovery from the storage system
  • Chemical properties
    1. Chemical stability
    2. Complete reversible freeze/melt cycle
    3. No degradation after a large number of freeze/melt cycle
    4. Non-corrosiveness, non-toxic, non-flammable and non-explosive materials
  • Economic properties
    1. Low cost
    2. Availability

Thermophysical properties of common PCMs[edit]

Material
Organic
PCM
Melting
point

oC
Heat of
fusion

kJ·kg−1
Heat of
fusion

MJ·m−3
Specific heat, cp
solid
kJ·kg−1·K−1
Specific heat, cp
liquid
kJ·kg−1·K−1
Density, ρ
solid
kg·m−3
Density, ρ
liquid
kg·m−3
Thermal conductivity, k
solid
W·m−1·K−1
VHC
solid
kJ·m−3·K−1
VHC
liquid
kJ·m−3·K−1
Thermal effusivity, e
solid
J·m−2·K−1·s−1/2
Cost
USD·kg−1
Water No 0 333.6 319.8 2.05 4.186 917 1,000 1.6[6]-2.22[7] 1,880 4,186 1,890 0.003125[8]
Sodium sulfate (Na2SO4·10H2O) No 32.4 252 0.05 [9]
NaCl·Na2SO4·10H2O No 18 286 0.05 [9]
Lauric acid Yes[10][11] 44.2[12] 211.6 197.7 1.76 2.27 1,007 862 1,772 1,957 1.6 [13][14]
TME(63%w/w)+H2O(37%w/w) Yes[10][11] 29.8 218.0 240.9 2.75 3.58 1,120 1,090 3,080 3,902
Mn(NO3)2·6H2O+MnCl2·4H2O(4%w/w) No[15][16] 15–25 125.9 221.8 2.34 2.78 1,795 1,728 4,200 4,804
Na2SiO3·5H2O No[15][16] 72.20 267.0 364.5 3.83 4.57 1,450 1,280 0.103−0.128[17] 5,554 5,850 801 8.04[18]
Aluminium No 660.32 396.9 1,007.2 0.8969 2,700 2,375 237[19][20] 2,422  ? 23,960 2.04626[21]
Copper No 1,084.62 208.7 1,769.5 0.3846 8,940 8,020 401[22] 3,438  ? 37,130 6.81256[23]
Gold No 1,064.18 63.72 1,166.3 0.129 19,300 17,310 318[24] 2,491 28,140 34,297.8[23]
Iron No 1,538 247.3 1,836.6 0.4495 7,874 6,980 80.4[25] 3,539 16,870 0.3248[26]
Lead No 327.46 23.02 253.2 0.1286 11,340 10,660 35.3[27] 1,459 7,180 2.1151[23]
Lithium No 180.54 432.2 226.0 3.5816 534 512 84.8[28] 1,913 12,740 62.2164[29]
Silver No 961.78 104.6 1,035.8 0.235 10,490 9,320 429[30] 2,465 32,520 492.524[23]
Titanium No 1,668 295.6 1,273.5 0.5235 4,506 4,110 21.9[31] 2,359 7,190 8.0469[32]
Zinc No 419.53 112.0 767.5 0.3896 7,140 6,570 116[33] 2,782 17,960 2.15735[23]
NaNO3 No 310 174 [34]
NaNO2 No 282 212 [34]
NaOH No 318 158 [34]
KNO3 No 337 116 [34]
KOH No 360 167 [34]
NaOH/ Na2CO3 (7.2%) No 283 340 [34]
NaCl(26.8%)/NaOH No 370 370 [34]
NaCl/KCL(32.4%)/LiCl(32.8%) No 346 281 [34]
NaCl(5.7%)/ NaNO3 (85.5%)/Na2SO4 No 287 176 [34]
NaCl/ NaNO3 (5.0%) No 284 171 [34]
NaCl(5.0%)/ NaNO3 No 282 212 [34]
NaCl(42.5%)/KCl(20.5)/MgCl2 No 385-393 410 [34]
KNO3(10%)/NaNO3 No 290 170 [34]
KNO3/KCl(4,5%) No 320 150 [34]
KNO3/KBr(4.7%)/KCl(7.3%) No 342 140 [34]
Paraffin 14-Carbons [35] Yes 5.5 228
Paraffin 15-Carbons [35] Yes 10 205
Paraffin 16-Carbons [35] Yes 16.7 237.1
Paraffin 17-Carbons [35] Yes 21.7 213
Paraffin 18-Carbons [35] Yes 28 244
Paraffin 19-Carbons [35] Yes 32 222
Paraffin 20-Carbons [35] Yes 36.7 246
Paraffin 21-Carbons [35] Yes 40.2 200
Paraffin 22-Carbons [35] Yes 44 249
Paraffin 23-Carbons [35] Yes 47.5 232
Paraffin 24-Carbons [35] Yes 50.6 255
Paraffin 25-Carbons [35] Yes 49.4 238
Paraffin 26-Carbons [35] Yes 56.3 256
Paraffin 27-Carbons [35] Yes 58.8 236
Paraffin 28-Carbons [35] Yes 61.6 253
Paraffin 29-Carbons [35] Yes 63.4 240
Paraffin 30-Carbons [35] Yes 65.4 251
Paraffin 31-Carbons [35] Yes 68 242
Paraffin 32-Carbons [35] Yes 69.5 170
Paraffin 33-Carbons [35] Yes 73.9 268
Paraffin 34-Carbons [35] Yes 75.9 269
Formic acid [35] Yes 7.8 247
Caprilic acid [35] Yes 16.3 149
Glycerin [35] Yes 17.9 198.7
p-Lattic acid [35] Yes 26 184
Methyl palmitate [35] Yes 29 205
Camphenilone [35] Yes 39 205
Docasyl bromide [35] Yes 40 201
Caprylone [35] Yes 40 259
Phenol [35] Yes 41 120
Heptadecanone [35] Yes 41 201
1-Cyclohexylooctadecane [35] Yes 41 218
4-Heptadacanone [35] Yes 41 197
p-Joluidine [35] Yes 43.3 167
Cyanamide [35] Yes 44 209
Methyl eicosanate [35] Yes 45 230
3-Heptadecanone [35] Yes 48 218
2-Heptadecanone [35] Yes 48 218
Hydrocinnamic acid [35] Yes 48 118
Cetyl acid [35] Yes 49.3 141
α-Nepthylamine [35] Yes 59 93
Camphene [35] Yes 50 238
O-Nitroaniline [35] Yes 50 93
9-Heptadecanone [35] Yes 51 213
Thymol [35] Yes 51.5 115
Methyl behenate [35] Yes 52 234
Diphenyl amine [35] Yes 52.9 107
p-Dichlorobenzene [35] Yes 53.1 121
Oxolate [35] Yes 54.3 178
Hypophosphoric acid [35] Yes 55 213
O-Xylene dichloride [35] Yes 55 121
β-Chloroacetic acid [35] Yes 56 147
Chloroacetic acid [35] Yes 56 130
Nitro napthalene [35] Yes 56.7 103
Trimyristin [35] Yes 33 201
Heptaudecanoic acid [35] Yes 60.6 189
α-Chloroacetic acid [35] Yes 61.2 130
Bee wax [35] Yes 61.8 177
Bees wax [35] Yes 61.8 177
Glyolic acid [35] Yes 63 109
Glycolic acid [35] Yes 63 109
p-Bromophenol [35] Yes 63.5 86
Azobenzene [35] Yes 67.1 121
Acrylic acid [35] Yes 68 115
Dinto toluent (2,4) [35] Yes 70 111
Phenylacetic acid [35] Yes 76.7 102
Thiosinamine [35] Yes 77 140
Bromcamphor [35] Yes 77 174
Durene [35] Yes 79.3 156
Benzylamine [35] Yes 78 174
Methly brombrenzoate [35] Yes 81 126
Alpha napthol [35] Yes 96 163
Glautaric acid [35] Yes 97.5 156
p-Xylene dichloride [35] Yes 100 138.7
Catechol [35] Yes 104.3 207
Quinone [35] Yes 115 171
Actanilide [35] Yes 118.9 222
Succinic anhydride [35] Yes 119 204
Benzoic acid [35] Yes 121.7 142.8
Stibene [35] Yes 124 167
Benzamide [35] Yes 127.2 169.4
Acetic acid [35] Yes 16.7 184
Polyethylene glycol 600 [35] Yes 20 146
Capric acid [35] Yes 36 152
Eladic acid [35] Yes 47 218
Pentadecanoic acid [35] Yes 52.5 178
Tristearin [35] Yes 56 191
Myristic acid [35] Yes 58 199
Palmatic acid [35] Yes 55 163
Stearic acid [35] Yes 69.4 199
Acetamide [35] Yes 81 241
Methyl fumarate [35] Yes 102 242

Volumetric heat capacity (VHC) J·m−3·K−1

VHC = \rho c_p

Thermal inertia (I) = Thermal effusivity (e) J·m−2·K−1·s−1/2

I = \sqrt{k\rho c_p} = e = {(k\rho c_p)}^{1/2}

Thermophysical properties of commercially available PCMs near room temperature[edit]

Material Supplier Type Form Melting
temperature, Tm

oC
Melting
temperature, Tm

oF
Latent heat
of fusion, L

kJ/kg
Density, ρ
kg/m3
Thermal
conductivity, k

W/m·K
Specific
heat, cp

kJ/kg·K
PureTemp -37 PureTemp [36] Organic Bulk -37 -35 147 880 1.39
PureTemp -23 PureTemp Organic Bulk -23 -9 145 860 2.11
PureTemp -21 PureTemp Organic Bulk -21 -6 240 1060 1.83
PureTemp -17 PureTemp Organic Bulk -17 1 145 860 1.74
PureTemp -15 PureTemp Organic Bulk -15 5 286 1030 1.84
PureTemp -12 PureTemp Organic Bulk -12 10 168 870 1.86
PureTemp -5 PureTemp Organic Bulk -5 23 150 860 1.66
PureTemp 1 PureTemp Organic Bulk 1 34 300 1000 2.32
PureTemp 4 PureTemp Organic Bulk 4 39 195 880 2.44
PureTemp 6 PureTemp Organic Bulk 6 43 170 860 1.56
PureTemp 8 PureTemp Organic Bulk 8 46 180 860 1.85
PureTemp 12 PureTemp Organic Bulk 12 54 185 860 1.76
PureTemp 15 PureTemp Organic Bulk 15 59 165 860 2.25
PureTemp 18 PureTemp Organic Bulk 18 64 189 860 1.47
PureTemp 20 PureTemp Organic Bulk 20 68 180 860 2.59
PureTemp 23 PureTemp Organic Bulk 23 73 203 830 1.84
PureTemp 24 PureTemp Organic Bulk 24 75 185 860 2.85
PureTemp 25 PureTemp Organic Bulk 25 77 185 860 1.99
PureTemp 27 PureTemp Organic Bulk 27 81 200 860 2.46
PureTemp 28 PureTemp Organic Bulk 29 84 205 860 2.34
PureTemp 29 PureTemp Organic Bulk 29 84 189 850 1.77
PureTemp 33 PureTemp Organic Bulk 33 91 185 850 2.34
PureTemp 35 PureTemp Organic Bulk 35 95 180 850 2.44
PureTemp 37 PureTemp Organic Bulk 38 100 222 840 2.21
PureTemp 48 PureTemp Organic Bulk 52 126 245 820 2.1
PureTemp 53 PureTemp Organic Bulk 53 127 225 990 2.36
PureTemp 58 PureTemp Organic Bulk 58 136 237 810 2.47
PureTemp 60 PureTemp Organic Bulk 61 142 230 870 2.04
PureTemp 63 PureTemp Organic Bulk 63 145 199 840 1.99
PureTemp 68 PureTemp Organic Bulk 68 154 198 870 1.85
PureTemp 103 PureTemp Organic Bulk 103 217 157 1220 2.09
PureTemp 151 PureTemp Organic Bulk 151 304 170 1360 2.06
Astorstat HA 17 Honey well [37] Organic Bulk 21.7 71
Astorstat HA 18 Honey well Organic Bulk 27.2 81
RT26 Rubitherm GmbH [38] Organic Bulk 24 75 232
RT27 Rubitherm GmbH Organic Bulk 28 82 206
Climsel C -21 Climator [39] Inorganic Bulk -21 -6 288 1300 0.6 3.6
Climsel C -18 Climator Inorganic Bulk -18 0 288 1300 0.6 3.6
Climsel C 7 Climator Inorganic Bulk 7 45 126 1400 0.6 3.6
Climsel C 10 Climator Inorganic Bulk 10.5 51 126 1400 0.6 3.6
Climsel C 21 Climator Inorganic Bulk 21 70 112 1380 0.6 3.6
Climsel C24 Climator Inorganic Bulk 24 75 151.3 1380 0.6 3.6
Climsel C28 Climator Inorganic Bulk 28 82 162.3 1420 0.6 3.6
Climsel C32 Climator Inorganic Bulk 32 90 162.3 1420 0.6 3.6
Climsel C48 Climator Inorganic Bulk 48 118 180 1360 0.6 3.6
Climsel C58 Climator Inorganic Bulk 58 136 288.5 1460 0.6 1.89
Climsel C70 Climator Inorganic Bulk 70 158 282.9 1400 0.6 3.6
STL27 Mitsubishi Chemicals [40] Inorganic Bulk 27 81 213
S27 Cristopia [41] Inorganic Bulk 27 81 207
TH 29 TEAP [42] Inorganic Bulk 29 84 188
RT 20 Rubitherm GmbH Organic Bulk 22 72 172
Climsel C23 Climator Inorganic Bulk 23 73 148 32
RT 26 Rubitherm GmbH Organic Bulk 25 77 131
STL 27 Mitsubishi Chemicals Inorganic Bulk 27 81 213
RT 30 Rubitherm GmbH Organic Bulk 28 82 206
RT 32 Rubitherm GmbH Organic Bulk 21 70 130
DS 5000 Micronal [43] Micro-encapsulated 26 79 45
DS 5007 Micronal Micro-encapsulated 23 73 41
DS 5030 Micronal Micro-encapsulated 21 70 37
DS 5001 Micronal Micro-encapsulated 26 79 110
DS 5008 Micronal Micro-encapsulated 23 73 100
DS 5029 Micronal Micro-encapsulated 21 70 90
RT -9 HC Rubitherm GmbH Organic Bulk -9 16 260
RT -4 Rubitherm GmbH Organic Bulk -4 25 179
RT 0 Rubitherm GmbH Organic Bulk 0 32 225
RT 2 HC Rubitherm GmbH Organic Bulk 2 36 205
RT 3 Rubitherm GmbH Organic Bulk 3 37 198
RT 3 HC Rubitherm GmbH Organic Bulk 3 37 250
RT 4 Rubitherm GmbH Organic Bulk 4 39 182
RT 5 Rubitherm GmbH Organic Bulk 5 41 180
RT 5 HC Rubitherm GmbH Organic Bulk 5 41 240
RT 6 Rubitherm GmbH Organic Bulk 6 43 175
RT 8 Rubitherm GmbH Organic Bulk 8 46 180
RT 9 Rubitherm GmbH Organic Bulk 9 48 160
RT 10 Rubitherm GmbH Organic Bulk 10 50 150
RT 10 HC Rubitherm GmbH Organic Bulk 10 50 195
RT 11 HC Rubitherm GmbH Organic Bulk 11 52 190
RT 12 Rubitherm GmbH Organic Bulk 12 54 150
RT 15 Rubitherm GmbH Organic Bulk 15 59 140
RT 18 HC Rubitherm GmbH Organic Bulk 18 64 250
RT 21 Rubitherm GmbH Organic Bulk 21 70 160
RT 21 HC Rubitherm GmbH Organic Bulk 21 70 190
RT 22 HC Rubitherm GmbH Organic Bulk 22 72 200
RT 24 Rubitherm GmbH Organic Bulk 24 75 150
RT 25 Rubitherm GmbH Organic Bulk 25 77 148
RT 25 HC Rubitherm GmbH Organic Bulk 25 77 230
RT 27 Rubitherm GmbH Organic Bulk 27 81 179
RT 28 HC Rubitherm GmbH Organic Bulk 28 82 245
RT 31 Rubitherm GmbH Organic Bulk 31 88 170
RT 35 Rubitherm GmbH Organic Bulk 35 95 170
RT 35 HC Rubitherm GmbH Organic Bulk 35 95 240
RT 42 Rubitherm GmbH Organic Bulk 42 108 174
RT 44 HC Rubitherm GmbH Organic Bulk 44 111 255
RT 47 Rubitherm GmbH Organic Bulk 47 117 170
RT 50 Rubitherm GmbH Organic Bulk 50 122 168
RT 52 Rubitherm GmbH Organic Bulk 52 126 173
RT 55 Rubitherm GmbH Organic Bulk 55 131 172
RT 58 Rubitherm GmbH Organic Bulk 58 136 160
RT 60 Rubitherm GmbH Organic Bulk 60 140 144
RT 62 Rubitherm GmbH Organic Bulk 62 144 146
RT 65 Rubitherm GmbH Organic Bulk 65 149 152
RT 70 HC Rubitherm GmbH Organic Bulk 70 158 230
RT 80 HC Rubitherm GmbH Organic Bulk 79 174 240
RT 82 Rubitherm GmbH Organic Bulk 82 180 176
RT 90 HC Rubitherm GmbH Organic Bulk 90 194 200
S117 PlusICE [44] Inorganic Bulk 117 243 160 1450 0.7 2.61
S89 PlusICE Inorganic Bulk 89 192 151 1550 0.67 2.48
S83 PlusICE Inorganic Bulk 83 181 141 1600 0.62 2.31
S72 PlusICE Inorganic Bulk 72 162 127 1666 0.58 2.13
S70 PlusICE Inorganic Bulk 70 158 110 1680 0.57 2.1
S58 PlusICE Inorganic Bulk 58 136 145 1505 0.69 2.55
S50 PlusICE Inorganic Bulk 50 122 100 1601 0.43 1.59
S46 PlusICE Inorganic Bulk 46 115 210 1587 0.45 2.41
S44 PlusICE Inorganic Bulk 44 111 100 1584 0.43 1.61
S34 PlusICE Inorganic Bulk 34 93 115 2100 0.52 2.1
S32 PlusICE Inorganic Bulk 32 90 200 1460 0.51 1.91
S30 PlusICE Inorganic Bulk 30 86 190 1304 0.48 1.9
S27 PlusICE Inorganic Bulk 27 81 183 1530 0.54 2.2
S25 PlusICE Inorganic Bulk 25 77 180 1530 0.54 2.2
S23 PlusICE Inorganic Bulk 23 73 175 1530 0.54 2.2
S21 PlusICE Inorganic Bulk 22 72 170 1530 0.54 2.2
S19 PlusICE Inorganic Bulk 19 66 160 1520 0.43 1.9
S17 PlusICE Inorganic Bulk 17 63 160 1525 0.43 1.9
S15 PlusICE Inorganic Bulk 15 59 160 1510 0.43 1.9
S13 PlusICE Inorganic Bulk 13 55 160 1515 0.43 1.9
S10 PlusICE Inorganic Bulk 10 50 155 1470 0.43 1.9
S8 PlusICE Inorganic Bulk 8 46 150 1475 0.44 1.9
S7 PlusICE Inorganic Bulk 7 45 150 1700 0.4 1.85
A164 PlusICE Organic Bulk 164 327 290 1500 2.42
A155 PlusICE Organic Bulk 155 311 100 900 0.23 2.2
A144 PlusICE Organic Bulk 144 291 115 880 0.23 2.2
A133 PlusICE Organic Bulk 133 271 126 880 0.23 2.2
A118 PlusICE Organic Bulk 118 244 340 1450 2.7
A95 PlusICE Organic Bulk 95 203 205 900 0.22 2.2
A82 PlusICE Organic Bulk 82 180 155 850 0.22 2.21
A70 PlusICE Organic Bulk 70 158 173 890 0.23 2.2
A62 PlusICE Organic Bulk 62 144 145 910 0.22 2.2
A60H PlusICE Organic Bulk 60 140 212 800 0.18 2.15
A60H PlusICE Organic Bulk 60 140 145 910 0.22 2.22
A58H PlusICE Organic Bulk 58 136 243 820 0.18 2.85
A58 PlusICE Organic Bulk 58 136 132 910 0.22 2.22
A55 PlusICE Organic Bulk 55 131 135 905 0.22 2.22
A53H PlusICE Organic Bulk 53 127 166 810 0.18 2.02
A53H PlusICE Organic Bulk 53 127 130 910 0.22 2.22
A52 PlusICE Organic Bulk 52 126 222 810 0.18 2.15
A50 PlusICE Organic Bulk 50 122 218 810 0.18 2.15
A48 PlusICE Organic Bulk 48 118 234 810 0.18 2.85
A46 PlusICE Organic Bulk 46 115 155 910 0.22 2.22
A44 PlusICE Organic Bulk 44 111 242 805 0.18 2.15
A43 PlusICE Organic Bulk 43 109 165 780 0.18 2.37
A42 PlusICE Organic Bulk 42 108 105 905 0.21 2.22
A40 PlusICE Organic Bulk 40 104 230 810 0.18 2.43
A39 PlusICE Organic Bulk 39 102 105 900 0.22 2.22
A37 PlusICE Organic Bulk 37 99 235 810 0.18 2.85
A36 PlusICE Organic Bulk 36 97 217 790 0.18 2.37
A32 PlusICE Organic Bulk 32 90 130 845 0.21 2.2
A29 PlusICE Organic Bulk 29 84 225 810 0.18 2.15
A28 PlusICE Organic Bulk 28 82 155 789 0.21 2.22
A26 PlusICE Organic Bulk 26 79 150 790 0.21 2.22
A25H PlusICE Organic Bulk 25 77 226 810 0.18 2.15
A25 PlusICE Organic Bulk 25 77 150 785 0.18 2.26
A24 PlusICE Organic Bulk 24 75 145 790 0.18 2.22
A23 PlusICE Organic Bulk 23 73 145 785 0.18 2.22
A22H PlusICE Organic Bulk 22 72 216 820 0.18 2.85
A22 PlusICE Organic Bulk 22 72 145 785 0.18 2.22
A17 PlusICE Organic Bulk 17 63 150 785 0.18 2.22
A16 PlusICE Organic Bulk 16 61 213 760 0.18 2.37
A15 PlusICE Organic Bulk 15 59 130 790 0.18 2.26
A9 PlusICE Organic Bulk 9 48 140 775 0.21 2.16
A8 PlusICE Organic Bulk 8 46 150 773 0.21 2.16
A6 PlusICE Organic Bulk 6 43 150 770 0.21 2.17
A4 PlusICE Organic Bulk 4 39 200 766 0.21 2.18
A3 PlusICE Organic Bulk 3 37 200 765 0.21 2.2
A2 PlusICE Organic Bulk 2 36 200 765 0.21 2.2
E0 PlusICE Eutectic Bulk 0 32 332 1000 0.58 4.19
E-2 PlusICE Eutectic Bulk -2 28 306 1070 0.58 3.8
E-3 PlusICE Eutectic Bulk -3.7 25 312 1060 0.6 3.84
E-6 PlusICE Eutectic Bulk -6 21 275 1110 0.56 3.83
E-10 PlusICE Eutectic Bulk -10 14 286 1140 0.56 3.33
E-11 PlusICE Eutectic Bulk -11.6 11 301 1090 0.57 3.55
E-12 PlusICE Eutectic Bulk -12.3 10 250 1110 0.56 3.47
E-14 PlusICE Eutectic Bulk -14.8 5 243 1220 0.53 3.51
E-15 PlusICE Eutectic Bulk -15 5 303 1060 0.53 3.87
E-19 PlusICE Eutectic Bulk -18.7 -2 282 1125 0.58 3.29
E-21 PlusICE Eutectic Bulk -20.6 -5 263 1240 0.51 3.13
E-22 PlusICE Eutectic Bulk -22 -8 234 1180 0.57 3.34
E-26 PlusICE Eutectic Bulk -26 -15 260 1250 0.58 3.67
E-29 PlusICE Eutectic Bulk -29 -20 222 1420 0.64 3.69
E-32 PlusICE Eutectic Bulk -32 -26 243 1290 0.56 2.95
E-34 PlusICE Eutectic Bulk -33.6 -28 240 1205 0.54 3.05
E-37 PlusICE Eutectic Bulk -36.5 -34 213 1500 0.54 3.15
E-50 PlusICE Eutectic Bulk -49.8 -58 218 1325 0.56 3.28
E-75 PlusICE Eutectic Bulk -75 -103 102 902 0.17 2.43
E-78 PlusICE Eutectic Bulk -78 -108 115 880 0.14 1.96
E-90 PlusICE Eutectic Bulk -90 -130 90 786 0.14 2.56
E-114 PlusICE Eutectic Bulk -114 -173 107 782 0.17 2.39
PCM-HS26N SAVENRG [45] Inorganic Bulk -26 -15 205 1200
PCM-HS23N SAVENRG Inorganic Bulk -23 -9 200 1180
PCM-HS10N SAVENRG Inorganic Bulk -10 14 220 1100
PCM-HS07N SAVENRG Inorganic Bulk -7 19 230 1120
PCM-HS01P SAVENRG Inorganic Bulk 0 32 290 1010
PCM-OM05P SAVENRG Organic Bulk 5 41 198 770
PCM-0M06P SAVENRG Organic Bulk 5.5 42 260 735
PCM-0M08P SAVENRG Organic Bulk 8 46 190 1050
PCM-0M11P SAVENRG Organic Bulk 11 52 260 1060
PCM-0M21P SAVENRG Organic Bulk 21 70 120 1050
PCM-H22P SAVENRG Inorganic Bulk 22 72 185 1540
PCM-HS24P SAVENRG Inorganic Bulk 24 75 185 1540
PCM-HS29P SAVENRG Inorganic Bulk 29 84 190 1550
PCM-OM32P SAVENRG Organic Bulk 32 90 235 870
PCM-OM35P SAVENRG Organic Bulk 35 95 197 870
PCM-HS34P SAVENRG Inorganic Bulk 34 93 150 1850
PCM-OM37P SAVENRG Organic Bulk 37 99 218 880
PCM-OM46P SAVENRG Organic Bulk 46 115 245 860
PCM-OM48P SAVENRG Organic Bulk 48 118 255 980
PCM-OM53P SAVENRG Organic Bulk 53 127 192 860
PCM-OM65P SAVENRG Organic Bulk 65 149 210 840
PCM-HS89P SAVENRG Inorganic Bulk 89 192 180 1540
MPCM -30 Microtek [46] Organic Micro-encapsulated -30 -22 145
MPCM -30D Microtek Organic Micro-encapsulated -30 -22 145
MPCM -10 Microtek Organic Micro-encapsulated -9.5 15 155
MPCM -10D Microtek Organic Micro-encapsulated -9.5 15 155
MPCM 6 Microtek Organic Micro-encapsulated 6 43 162
MPCM 6D Microtek Organic Micro-encapsulated 6 43 162
MPCM 18 Microtek Organic Micro-encapsulated 18 64 168
MPCM 18D Microtek Organic Micro-encapsulated 18 64 168
MPCM 28 Microtek Organic Micro-encapsulated 28 82 187.5
MPCM 28D Microtek Organic Micro-encapsulated 28 82 187.5
MPCM28D-IR Microtek Organic Micro-encapsulated 56 133 170
MPCM 37 Microtek Organic Micro-encapsulated 37 99 195
MPCM 37D Microtek Organic Micro-encapsulated 37 99 195
MPCM 43D Microtek Organic Micro-encapsulated 43 109 195
MPCM 56D Microtek Organic Micro-encapsulated 56 133 170
Latest 29 T TEAP Inorganic Bulk 28 82 175 1490 1 2
Latest 25 T TEAP Inorganic Bulk 24 75 175 1490 1 2
Latest 20 T TEAP Inorganic Bulk 19 66 175 1490 1 2
Latest 18 T TEAP Inorganic Bulk 17 63 175 1490 1 2

The above dataset is also available as an Excel spreadsheet from UCLA Engineering

Technology, development and encapsulation[edit]

The most commonly used PCMs are salt hydrates, fatty acids and esters, and various paraffins (such as octadecane). Recently also ionic liquids were investigated as novel PCMs.

As most of the organic solutions are water-free, they can be exposed to air, but all salt based PCM solutions must be encapsulated to prevent water evaporation or uptake. Both types offer certain advantages and disadvantages and if they are correctly applied some of the disadvantages becomes an advantage for certain applications.

They have been used since the late 19th century as a medium for the thermal storage applications. They have been used in such diverse applications as refrigerated transportation[47] for rail[48] and road applications[49] and their physical properties are, therefore, well known.

Unlike the ice storage system, however, the PCM systems can be used with any conventional water chiller both for a new or alternatively retrofit application. The positive temperature phase change allows centrifugal and absorption chillers as well as the conventional reciprocating and screw chiller systems or even lower ambient conditions utilizing a cooling tower or dry cooler for charging the TES system.

The temperature range offered by the PCM technology provides a new horizon for the building services and refrigeration engineers regarding medium and high temperature energy storage applications. The scope of this thermal energy application is wide ranging of solar heating, hot water, heating rejection, i.e. cooling tower and dry cooler circuitry thermal energy storage applications.

Since PCMs transform between solid–liquid in thermal cycling, encapsulation[50] naturally become the obvious storage choice.

  • Encapsulation of PCMs
    • Macro-encapsulation: Early development of macro-encapsulation with large volume containment failed due to the poor thermal conductivity of most PCMs. PCMs tend to solidify at the edges of the containers preventing effective heat transfer.
    • Micro-encapsulation: Micro-encapsulation on the other hand showed no such problem. It allows the PCMs to be incorporated into construction materials, such as concrete, easily and economically. Micro-encapsulated PCMs also provide a portable heat storage system. By coating a microscopic sized PCM with a protective coating, the particles can be suspended within a continuous phase such as water. This system can be considered a phase change slurry (PCS).
    • Molecular-encapsulation is another technology, developed by Dupont de Nemours that allows a very high concentration of PCM within a polymer compound. It allows storage capacity up to 515 kJ/m2 for a 5 mm board (103 MJ/m3). Molecular-encapsulation allows drilling and cutting through the material without any PCM leakage.

As phase change materials perform best in small containers, therefore they are usually divided in cells. The cells are shallow to reduce static head – based on the principle of shallow container geometry. The packaging material should conduct heat well; and it should be durable enough to withstand frequent changes in the storage material's volume as phase changes occur. It should also restrict the passage of water through the walls, so the materials will not dry out (or water-out, if the material is hygroscopic). Packaging must also resist leakage and corrosion. Common packaging materials showing chemical compatibility with room temperature PCMs include stainless steel, polypropylene and polyolefin.

Thermal composites[edit]

Thermal-composites is a term given to combinations of phase change materials (PCMs) and other (usually solid) structures. A simple example is a copper-mesh immersed in a paraffin-wax. The copper-mesh within parraffin-wax can be considered a composite material, dubbed a thermal-composite. Such hybrid materials are created to achieve specific overall or bulk properties.

Thermal conductivity is a common property which is targeted for maximisation by creating thermal composites. In this case the basic idea is to increase thermal conductivity by adding a highly conducting solid (such as the copper-mesh) into the relatively low conducting PCM thus increasing overall or bulk (thermal) conductivity. If the PCM is required to flow, the solid must be porous, such as a mesh.

Solid composites such as fibre-glass or kevlar-pre-preg for the aerospace industry usually refer to a fibre (the kevlar or the glass) and a matrix (the glue which solidifies to hold fibres and provide compressive strength). A thermal composite is not so clearly defined, but could similarly refer to a matrix (solid) and the PCM which is of course usually liquid and/or solid depending on conditions. They are also meant to discover minor elements in the earth.

Applications[edit]

Applications[1][51] of phase change materials include, but are not limited to:

  • Thermal energy storage
  • Conditioning of buildings, such as 'ice-storage'
  • Cooling of heat and electrical engines
  • Cooling: food, beverages, coffee, wine, milk products, green houses
  • Medical applications: transportation of blood, operating tables, hot-cold therapies
  • Human body cooling under bulky clothing or costumes.
  • Waste heat recovery
  • Off-peak power utilization: Heating hot water and Cooling
  • Heat pump systems
  • Passive storage in bioclimatic building/architecture (HDPE, paraffin)
  • Smoothing exothermic temperature peaks in chemical reactions
  • Solar power plants
  • Spacecraft thermal systems
  • Thermal comfort in vehicles
  • Thermal protection of electronic devices
  • Thermal protection of food: transport, hotel trade, ice-cream, etc.
  • Textiles used in clothing
  • Computer cooling
  • Turbine Inlet Chilling with thermal energy storage
  • Telecom shelters in tropical regions. They protect the high-value equipment in the shelter by keeping the indoor air temperature below the maximum permissible by absorbing heat generated by power-hungry equipment such as a Base Station Subsystem. In case of a power failure to conventional cooling systems, PCMs minimize use of diesel generators, and this can translate into enormous savings across thousands of telecom sites in tropics.

Fire and safety issues[edit]

Some phase change materials are suspended in water, and are relatively nontoxic. Others are hydrocarbons or other flammable materials, or are toxic. As such, PCMs must be selected and applied very carefully, in accordance with fire and building codes and sound engineering practices. Because of the increased fire risk, flamespread, smoke, potential for explosion when held in containers, and liability, it may be wise not to use flammable PCMs within residential or other regularly occupied buildings. Phase change materials are also being used in thermal regulation of electronics.

See also[edit]

References[edit]

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Further reading[edit]